What to do this week –
By Mark Govan, Host “Florida Gardening“
Over the last few weeks, the weather has been pretty chilly, and as we delve further into our Holiday Season, we can count on several bouts with even colder temperatures with the possibility of a freeze. This change in temperatures can be helpful to some of our plants, but there are other landscape plants that may develop problems that you should be on the lookout for. Orchids and tropical plants do not like cool weather and need protection when temperatures fall below forty-five degrees. However, citrus trees like the cooler weather as this help them to increase the sugar content in the fruit. Because many of us do not know which plants to protect and which plants to leave alone, this week I am going to go over a few of the most common plant issues you may be dealing with right now.
If you are growing winter annuals like Dianthus, Petunias, Snapdragons, Violets, and Violas, and you are worried about them freezing, then you should apply a thick layer of mulch around these plants now. Mulch can help protect your plants root systems from freezing by providing a barrier against the cold. Even if the plants leaves are damaged by the cold, the root system will be able to help the plants recover much faster once temperatures rise. Be sure to add at least three inches of mulch from pine straw, pine bark, or cypress mulch over the entire root system.
Never place mulch directly next to the stems of plants or trees as this may allow fungal pathogens entry into the stem. Any open wound at the base of a plant can be susceptible to diseases and as the mulch decays, fungus could enter the plant. Another benefit to the mulch is its water-holding capacity. Mulch helps retain moisture the plants desperately need during times of drought or water restrictions. When the mulch breaks down over time, you will also receive the added benefit of organic matter being returned to the soil.
Mulch can also give your landscape that clean look. I recommend that mulch be renewed at least once yearly and preferably before a freeze in the fall. All of your ornamental plants in the landscape can benefit from a three-inch layer of mulch applied over the root system. Citrus trees and other fruit-bearing tress should not be mulched. Mulch added beneath fruit trees can cause root problems and in some cases will provide the base for a fungal pathogen to enter the plant.
Camellias, Azaleas, and Poinsettias all like the cold weather so do not worry about protecting them, unless we have a hard freeze. This is also the time of the year these three plants should be going into bloom or setting their blossoms, so make sure you do not prune them. Hibiscus, Plumerias, and Tropical flowering vines do not like the cold, and you may have noticed some of them have begun to drop their leaves. Many tropical plants drop their leaves this time of the year but do not be alarmed. These plants will rebound once the temperatures warm back up in the spring. Remember, tropical plants start showing signs of stress as temperatures fall below forty-five degrees, however, some plants need cool temperatures.
Temperatures below forty-five degrees start the clock on the chilling requirements fruiting plants need to produce their crops. Peaches, Nectarines, Apples, and even Blueberries need a certain amount of hours below forty-five degrees in order to produce. Many of the fruiting plants you purchase in the local garden centers will display a tag indicating the number of chilling hours required for that plant to set their crop. If you live in central Florida, and you want to grow one of the fruiting plants I listed above, then you will have to look for cultivars, which require the least amount of chilling hours. When possible, look for trees that require less than one hundred and fifty hours of chilling. Those of you whom select trees that require more than one hundred fifty hours of chilling, risk purchasing a plant that may grow, but will never produce fruit.
I have talked to dozens of people whom have purchased fruit trees that should be planted up north; these trees will never produce fruit in Central Florida. Some trees require over a thousand hours of chilling time, and we will never have that many hours below forty-five degrees in this part of the state. Again, the tree may grow fine, but you will not reap the benefit of fruit. An easy way to find the varieties of fruiting trees you need to purchase is to call the Cooperative Extension Office in your area. There is no charge for this service, and they can be very helpful in giving you information on gardening as well. If you have a home in our northern counties, or possibly in interior counties of Central Florida, then you may select trees or shrubs that require up to three hundred hours of chilling time.
Citrus trees like the cool weather and as long as we do not get a hard freeze, the cooler the weather is, the sweeter the fruit will be. Some people think that the cool weather breaks down the structure in the fruit making the fruit sweeter to the taste. This may sound bad, but the taste is what counts. Freezing temperatures, on the other hand, can break down the juice sacs in oranges or grapefruit. This can cause the fruit to rot as temperatures increase, so we do not want a prolonged freeze. Because many of our juice oranges are near harvest time when temperatures reach their lowest, you must be especially vigilant to monitor your fruit and use them in the kitchen when they are ready. Pick a few fruits from your tree when they look ready and do not rely on the color of the fruit to determine ripeness.
Some of our fruit may not be the color you think they should be when you harvest, but the fruit is ready to be eaten. This is a common mistake some people make who grow Navel oranges. Navels are usually ripe and ready for picking around Thanksgiving. Even though the skin of the fruit may still be yellow, the fruit is ripe and should be picked. Red Navels, Orange Navels, and Hamlin oranges are all ripe now. Remember, do not pick all your fruit at one time, the best place to store your fruit is on the tree. Strawberries are another crop that cool weather has an impact on.
Cool weather helps strawberries increase their sugar content. Unfortunately, a freeze can be devastating to strawberries. When the weather person states that we are going to have a freeze tonight, the growers turn on their sprinklers to coat the strawberries with a layer of ice to protect the plants and the ripening berries. If you are growing strawberries, then you too will have to protect them from the freeze. There are products available to help you protect your fruits and vegetables such as frost blankets, and a new product called Freeze Pruf. Freeze Pruf is a liquid that can be sprayed directly on your plants. This eco-safe spray improves the plants natural cold tolerance by up to 9 degrees. You can look up Freeze Pruf on the Internet at the following address http://www.liquidfence.com/FreezePruf.html. Materials like Freeze Pruf will need to be re-applied every month during cold weather.
Frost blankets are also available at most retail garden centers. I have even seen them at the local box stores. Make sure that if you are going to cover your plant with one of these, that you cover the entire plant to the ground. Covering to the ground helps retain heat let off from the soil during the night and circulates it around your plant. The addition of a light bulb or other heat source during the night can help maintain temperature under the blanket, especially during windy nights. Use a little soil around the base of the blanket to ensure a tight seal. Never use plastic blankets around your plants. Plastic intensifies the cold and when left on the plant during the day, many plants can be burned by the warm temperatures which build-up in the afternoon.
The last thing I want to talk about here is your turf grass. Winter Brown Patch or Rhizoctonia is a fungus disease that can cause major damage to our St. Augustine lawns. Look for areas of the lawn that turn brown and in many cases, appear to grow in a circle. As the disease spreads, these small circular patterns seem to coalesce into large areas. Sometimes, the areas in the center of the patches may look like they are recovering. However, this disease spreads very quickly and the most active areas of the fungus are at the outer edges of the circle. These outer edges normally have a yellow hue to them and may give off an odor of decay you can smell. Homeowners should walk their lawns weekly to look for this disease before it spreads. Call your pest management professional to treat this disease before you lose your lawn.
Cooler temperatures can be both good and bad for our landscapes. If you grow many tropical plants, then you will be spending some nights working to protect them. Mulch can be an asset you can utilize to help your plants survive even the coldest nights. Some of our cold-hardy plants will need little extra attention from you. Always choose plants based on the area of Florida you live in, and if you are selecting fruiting plants, then make sure those plants are approved for your area. Good luck with your garden, and remember, without plants, we would not be here!